The Comparison of Three Sample Pretreatment Methods in Determination of Gallium in Bauxite Ores by Inductively Coupled Plasma-Atomic Emission Spectrometry

The bauxite ores were digested by three different pretreatments as HCl-HNO₃-HF-HClO₄ mixed acids, HF-HNO₃-H₂SO₄ mixed acids and alkali fusion. The Ga was measured by Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES). The HCl-HNO₃-HF-HClO₄ mixed acids incompletely dissolved the bauxite ores with a large amount of residues. Due to the Ga reacts with HCl to form GaCl₃ which is easy to volatilize from the solution system, the measured Ga concentration is much lower than the certified value. The bauxite ores also were incompletely dissolved by HF-HNO₃-H₂SO₄ mixed acids with lower concentration for Ga. Nevertheless, the bauxite ores were completely digested by alkali fusion with clear solution. The NaCl in solution can protect Ga lossing by volatilization to obtain accurate result. The method of alkali fusion, HCl extraction and measurement by ICP-AES produces high precision and accurate result for Ga with detection limit of 3.21 μg/g and less than 5% RSD (n=11). The obtained result is generally consistent with certified value of both first and second grade national standard reference materials.